Is North Korea a Threat to the United States?

When is enough enough; does North Korea pose a real threat to the United States? The following short video shows the supposed ballistic missile threat by North Korea.

In the past North Korea has always backed off, due to concessions and sanctions made by the United States and the United Nations, after making threats of war. The concessions made by Kim Jong-il due to these actions of the US and UN were solely for his own benefit and the benefit of his army, not for the benefit of his country’s people.

I feel, as do many others, that the actions and threats of North Korea are now being controlled by something other than Kim Jong-il’s own maniacal ego. Who or what is currently fueling his need for war?